This application claims the benefit of Japanese Patent Application No. 2000-089048 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an improvement in a rotation transmitting device incorporating a one-way clutch therein which can be used typically as a driven pulley fixed to an end of a rotary shaft of an alternator which serves as a power generator in a car, or a pinion fixed to an end of a rotary shaft for constituting a starter motor of a starting system of a car.
2. Related Background Art
The structure of an alternator which generates electric power necessary for a car by using an engine of the car as its driving source is disclosed, for instance, in Japanese Patent Application Laid-Open No. 7-139550. FIG. 6 illustrates an alternator 1 which is described in the above application. Referring to FIG. 6, a rotary shaft 3 is rotatably supported by a pair of rolling bearings 4 and 4 inside a housing 2. A rotor 5 and a rectifier 6 are provided in a middle part of this rotary shaft 3. In addition, a driven pulley 7 is fixed to an end portion (the right end portion in FIG. 6) of this rotary shaft 3 which is protruded outward from the housing 2. In a state in which the alternator is assembled in the engine, an endless belt is wound around this driven pulley 7 so that the rotary shaft 3 is driven to rotate freely by means of a crank shaft of the engine.
As the driven pulley 7 described above, a pulley which is simply fixed to the rotary shaft 3 has been conventionally employed. However, various types of a pulley device incorporating a one-way clutch therein have been recently proposed as rotation transmitting devices incorporating a one-way clutch therein which are arranged to transmit the driving power from the endless belt to the rotary shaft when the running speed of the endless belt is fixed or on the increase, while allowing relative rotation between the driven pulley and the rotary shaft when the running speed of the endless belt is on the decrease. Some of such pulley devices have been put into practice use. For instance, pulley devices incorporating a one-way clutch therein and having a function as described above are disclosed in Japanese Patent Application Laid-Open Nos. 56-101353, 7-317807, 8-61443, 8-226462 and 7-72585, French Patent Publication FR2726059A1, and the like.
FIGS. 7 to 9 illustrate a pulley device incorporating a one-way clutch conventionally known by being described in either of the above publications. This pulley device incorporating a one-way clutch therein comprises a sleeve 8 which serves as an inner diameter side member and can be fitted and fixed onto the rotary shaft 3 of the alternator 1 (see FIG. 6). Around this sleeve 8, there is provided a driven pulley 7a which serves as an outer diameter side member in a cylindrical form to be concentric with this sleeve 8. Then, a pair of support bearings 9, 9 and a roller clutch 10 serving as the one-way clutch are provided between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the driven pulley 7a. 
The sleeve 8 is formed to be cylindrical as a whole, and is fitted and fixed onto an end portion of the rotary shaft 3 of the alternator 1 to be rotatable with this rotary shaft 3. To this end, in the illustrated example, a threaded hole portion 11 is formed in a middle part on the inner peripheral surface of the sleeve 8, and this threaded hole portion and a male screw portion which is formed on the outer peripheral surface at the tip end portion of the rotary shaft 3 are arranged to be thread-engaged with each other. A latch hole portion 12 having a hexagonal cross section is also formed at the tip end portion on the inner peripheral surface of the sleeve 8 (the left end portion in FIG. 7). The tip end portion of a tool such as a hexagonal wrench can be latched by this latch hole portion 12. Furthermore, the base portion (the right end portion in FIG. 7) of the inner peripheral surface of the sleeve 8 serves as a circular hole portion 13 which can be fitted on a portion near the middle part of the tip end portion of the rotary shaft 3 with no play. Note that a spline engagement, non-circular fitting, key engagement, or another arrangement may be employed as the arrangement for combining the sleeve 8 with the rotary shaft 3 in such a manner that they are not relatively rotated with each other. In addition, the central portion of the outer peripheral surface of the sleeve 8 serves as a large diameter portion 14 which has a larger diameter size than that of another portion.
On the other hand, a tip half portion of the outer peripheral surface of the driven pulley 7a has a cross section in a waveform along the widthwise direction, around which a part of the endless belt called a poly-V belt can be wound. Then, the above-mentioned roller clutch 10 is disposed in a middle part in the axial direction of a space existing between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the driven pulley 7a, while the support bearings 9, 9 are respectively disposed at positions to sandwich this roller clutch 10 from the both sides in the axial direction near the both ends of this space in the axial direction.
Out of these members, the support bearings 9, 9 allow, while supporting a radial load applied on the driven pulley 7a, a relative rotation between this driven pulley 7a and the sleeve 8. In the illustrated example, ball bearings of a deep groove type are used as the support bearings 9, 9. More specifically, these support bearings 9, 9 comprise outer races 16, 16 respectively having outer raceways 15, 15 of the deep groove type on the respective inner peripheral surfaces thereof, inner races 18, 18 respectively having inner raceways 17, 17 of the deep groove type on the respective outer peripheral surfaces thereof, and balls 19, 19 provided in plural sets as capable of rolling between the outer raceways 15, 15 and the inner raceways 17, 17. Then, the outer races 16, 16 are fitted and fixed onto the inner peripheral surface near the both ends of the driven pulley 7a, while the inner races 18, 18 are onto the outer peripheral surfaces near the both ends of the sleeve 8, respectively. In this state, the inner races 18, 18 in the axial direction are brought into contact with the respective end surfaces (step surfaces) in the axial direction of the large diameter portion 14. Also, in the illustrated example, seal rings 20, 20 are provided between the inner peripheral surfaces of the both end portions of the outer races 16, 16 and the outer peripheral surfaces of the both end portions of the inner races 18, 18, respectively, thereby sealing openings at the both ends of the space provided with the balls 19, 19 described above.
It is preferable that a communication hole is formed in a part of each of the seal rings 20, 20 on the side facing a space which is formed by and between the support bearings 9, 9, out of the above-described seal rings 20, 20, so that this space and the space receiving therein the balls 19, 19 of the support bearings 9, 9 are communicated to each other, in order to prevent excessive rise of the pressure inside the space formed by and between the support bearings 9, 9 when the support bearings 9, 9 are inserted with pressure between the inner peripheral surface of the driven pulley 7a and the outer peripheral surface of sleeve 8. When the outer races 16, 16 are interference-fitted and fixed into the inner peripheral surface of the driven pulley 7a, it is preferable that, out of the inner peripheral surface of this driven pulley 7a, a part in which the outer races 16, 16 are fitted is made a large diameter portion, while a part in which a clutch outer race 25, which is described later, is fitted is made a small diameter portion, so that the large diameter portion and the small diameter portion are in a stepped form continued by the paired step surfaces, since a flaw in a groove shape is easily created along the axial direction on the inner peripheral surface of the driven pulley 7a when the clutch outer race 25 is thrust into the inner peripheral surface of this driven pulley 7a in case that the inner peripheral surface of the driven pulley 7a is a single cylindrical surface. Then, when such a groove is created, there is a possibility that the grease enclosed in the gap between the both support bearings 9, 9 is leaked out through the gap between the groove and the outer peripheral surfaces of the outer races 16, 16. On the contrary, if the size of a part in which the clutch outer race 25 is fitted is set to be smaller than that of a part in which the outer races 16, 16 are fitted, such a flaw as described above can be prevented.
The roller clutch 10 is arranged to allow transmission of the force of rotation between the driven pulley 7a and the sleeve 8 only when the driven pulley 7a has a tendency to rotate in a predetermined direction relatively to the sleeve 8. In order to arrange the roller clutch 10 as described above, the clutch inner race 21 is interference-fitted and fixed onto the large diameter portion 14 of the sleeve 8. This clutch inner race 21 is formed to be cylindrical as a whole by press working, or other plastic working, of a steel plate of, for instance, cemented steel, and on the outer surface of which, a cam surface 22 is formed. More specifically, a plurality of concave portions 23, 23 each called a ramp portion are formed on the outer peripheral surface of the clutch inner race 21 at regular intervals in the circumferential direction, whereby the outer peripheral surface serves as the cam surface 22 mentioned above. Note that, in the illustrated example, a concave chamfered portion 24 is formed on one end portion (the left end portion in FIG. 7) on the inner peripheral surface of the clutch inner race 21, and this chamfered portion 24 serves as a guide surface when the clutch inner race 21 is to be thrust with pressure into the outer peripheral surface of the large diameter portion 14.
On the contrary, out of the inner peripheral surface of the clutch outer race 25 which is interference-fitted and fixed in the middle part on the inner peripheral surface of the driven pulley 7a, at least a middle part in the axial direction in contact with rollers 26, which is described later, is simply formed as a cylindrical surface. Such clutch outer race 25 is formed to be cylindrical as a whole also by press working or other plastic working of a steel plate of, for instance, cemented steel, and inward flange portions 27a and 27b are formed at the both ends of the clutch outer race 25 in the axial direction. Note that one flange portion 27a (the left one in FIG. 7) out of the two flange portions 27a and 27b is formed prior to the manufacturing of the clutch outer race 25, so that this flange portion 27a has the thickness equal to that of the cylindrical portion of the clutch outer race 25. On the other hand, the other flange portion 27b (the right one in FIG. 7) is formed after a roller 26 which is described later and the clutch retainer 28 are assembled in the clutch outer race 25 inward in the radial direction. Consequently, the flange portion 27b is formed thin.
A plurality of rollers 26 for constituting the roller clutch 10 together with the clutch inner race 21 and the clutch outer race 25 are supported to allow a slight displacement in the rolling and circumferential directions by a clutch retainer 28 which is fitted on the clutch inner race 21 to allow no rotation with respect to the clutch inner race 21. This clutch retainer 28 is formed in a cylindrical form of a cage type as a whole of synthetic resin (for instance, synthetic resin of polyamide 66, polyamide 46, polyphenylene sulfide, or the like, mixed with 20% of glass fiber). This clutch retainer 28 is provided with a pair of rim portions 29, 29 each formed in an annular shape, and a plurality of column portions 30, 30 for connecting the both rim portions 29, 29 to each other.
Portions surrounded on the four sides by the inner side surfaces of the rim portions 29, 29 and the side surfaces of the column portions 30, 30 in the circumferential direction are called the pockets 31, 31 for holding the rollers 26 to allow a slight displacement in the rolling and circumferential directions. Then, arcuate convex portions 32, 32 which are formed at a plurality of positions on the inner peripheral surfaces of the rim portions 29, 29 are engaged with the concave portions 23, 23 formed on the outer peripheral surface of the clutch inner race 21, whereby the clutch retainer 28 is attached to the clutch inner race 21 in such a manner that a relative rotation with this clutch inner race 21 is not allowed.
Between the column portions 30, 30 for constituting this clutch retainer 28 and the rollers 26, there are provided, respectively, leaf springs or springs each typically made of a synthetic resin and integrally formed with this clutch retainer 28. These springs elastically press the respective rollers 26 in the same direction with respect to the circumferential direction of the clutch retainer 28 toward a portion, out of a cylindrical gap formed between the outer peripheral surface of the cam surface 22 and the inner peripheral surface (cylindrical surface) of a middle part of the clutch outer race 25, which is narrower in the radial direction. The both end surfaces in the axial direction of the clutch retainer 28 as described above are approximated to face the inner side surfaces of the two flange portions 27a, 27b for constituting the clutch outer race 25, thereby preventing a displacement of this clutch retainer 28 in the axial direction.
By the use of the pulley device incorporating a one-way clutch arranged as described above, when the driven pulley 7a and the sleeve 8 have a tendency to rotate relatively to each other in a predetermined direction, each roller 29 enters into the narrower portion in the radial direction of the cylindrical gap, whereby the relative rotation between the driven pulley 7a and the sleeve 8 becomes impossible (in a locked state). On the other hand, when the driven pulley 7a and the sleeve 8 are rotated relatively to each other in a direction opposite to the predetermined direction, each of the rollers 26 is retracted to a portion having the greater width in the radial direction of the cylindrical gap, thereby allowing the relative rotation between the driven pulley 7a and the sleeve 8 (in an over-run state).
There are two reasons for employing the pulley device incorporating a one-way clutch for an alternator having a structure as described above, as described below. The first reason is to prolong the life of the endless belt. For instance, by the use of a diesel engine as the driving engine, a fluctuation in angular speed of rotation of the crank shaft becomes great at the time of low rotation such as an idling time. As a result, the running speed of the endless belt which is wound around the driving pulley fluctuates finely On the other hand, the rotary shaft 3 of the alternator which is driven to rotate through the driven pulley by the use of this endless belt does not fluctuate so rapidly owing to the inertia masses of the rotary shaft 3 and a rotor, or the like, fixed to this rotary shaft 3. Thus, when the driven pulley is merely fixed to the rotary shaft, the endless belt and the driven pulley are inclined to rub each other in the both directions upon a fluctuation in the angular speed of rotation of the crank shaft. As a result, the stress works on the endless belt which rubs this driven pulley repeatedly in different directions, to easily cause a slip between this endless belt and the driven pulley, or to reduce the life of this endless belt.
Accordingly, by employing the pulley device incorporating a one-way clutch for an alternator having a structure as described above as the driven pulley described above, it is arranged such that the force of rotation can be transmitted from the driven pulley to the rotary shaft 3 when the running speed of the endless belt is fixed or on the increase, while the relative rotation is allowed between the driven pulley and the rotary shaft 3 when the running speed of the endless belt is on the decrease. More specifically, when the running speed of the endless belt is on the decrease, the angular speed of rotation of the driven pulley is set to be slower than the angular speed of rotation of the rotary shaft so as to prevent strong friction between the endless belt and the driven pulley in a contact portion therebetween. Thus, the direction of the stress acting on the frictional portion between the driven pulley and the endless belt is fixed so as to prevent a slip between this endless belt and the driven pulley or reduction of the life of this endless belt.
The second reason is to enhance the efficiency in power generation by the alternator. The rotary shaft 3 to which the rotor of the alternator is fixed is driven to rotate by the driving engine of the car through the endless belt and the driven pulley. When a driven pulley of a fixed type is used, if the speed of rotation of the driving engine is rapidly decreased, the speed of rotation of the rotor is also rapidly decreased, whereupon an amount of power generation by the alternator also rapidly decreases. On the contrary, when the pulley device incorporating a one-way clutch for an alternator described above is used as a driven pulley to be attached to the alternator, even if the speed of rotation of the driving engine is rapidly decreased, the speed of rotation of the rotor is gradually decreased due to the force of inertia, and the alternator continues to generate power all the time. As a result, compared with a case in which the driven pulley of a fixed type is used, the kinetic energies of the rotary shaft and the rotor can be effectively utilized, so as to increase an amount of power generation by the alternator.
With the conventional structure described above, the displacement of the clutch retainer 28 in the axial direction is prevented by the paired flange portions 27a, 27b which are provided at the both ends of the clutch outer race 25. More specifically, when the clutch retainer 28 is to be displaced in the axial direction at the time of over-run at which the driven pulley 7a and the sleeve 8 are rotated relatively to each other, an end surface in the axial direction of this clutch retainer 28 and the inner side surface of one 27a (or 27b) of the paired flange portions are brought into contact (sliding contact) to prevent the displacement in the axial direction of the clutch retainer 28. However, in case of the pulley device incorporating a one-way clutch for an alternator as described above, a relative speed of rotation between the pulley 7a and the sleeve 8 may reach several hundred minxe2x88x921 (r.p.m.) to several thousand minxe2x88x921 (r.p.m.) in an extreme case. For this reason, if the both end surfaces in the axial direction of the clutch retainer 28 and the inner side surfaces of the flange portions 27a, 27b are brought into sliding contact as described above, the both end surfaces in the axial direction of the clutch retainer 28 may be easily worn away, or a frictional heat which is generated in the sliding contact portions between the both end surfaces in the axial direction of this clutch retainer 28 and the inner side surfaces of the flange portions 27a, 27b may be excessively high.
Then, when abraded powder which is generated due to the abrasion of the both end surfaces in the axial direction of the clutch retainer 28 is mixed into the grease for lubricating the roller clutch 10, there is a possibility that the lubricating performance of this grease may be deteriorated. Also, when the frictional heat generated in the sliding contact portions becomes excessively high, the grease may be deteriorated by the heat in an early stage. The deterioration of the grease may cause a damage to the durability of the roller clutch 10 undesirably. Note that such a problem occurs in the same manner in a structure which does not comprise the pair of flange portions 27a, 27b even when the both end surfaces in the axial direction of the clutch retainer 28 are brought into sliding contact with another member which is rotated relatively to this clutch retainer 28.
The rotation transmitting device incorporating a one-way clutch therein according to the present invention has been contrived taking the circumstances as described above into consideration.
According to the present invention, there is provided a rotation transmitting device incorporating a one-way clutch therein which comprises, an inner diameter side member fixed to an end of a rotary shaft, an outer diameter side member in a cylindrical form disposed around the inner diameter side member to be concentric with the inner diameter side member, a one-way clutch disposed between a middle part in the axial direction on the outer peripheral surface of the inner diameter side member and a middle part in the axial direction on the inner peripheral surface of the outer diameter side member for transmitting rotation between the outer diameter side member and the inner diameter side member only when the outer diameter side member has a tendency to relatively rotate in a predetermined direction with respect to the inner diameter side member, and a pair of support bearings disposed between the outer peripheral surface of the inner diameter side member and the inner peripheral surface of the outer diameter side member at a position to pinch this one-way clutch from the both sides thereof in the axial direction for allowing a relative rotation between the inner diameter side member and the outer diameter side member while supporting a radial load applied on this outer diameter side member.
Specifically, in the rotation transmitting device incorporating a one-way clutch therein, a clutch retainer for constituting the one-way clutch is arranged, based on that a part of the peripheral surface of this clutch retainer is brought into engagement directly or through another member with either one of the inner peripheral surface of the outer diameter side member and the outer peripheral surface of the inner diameter side member, to be rotated together with a member disposed on the one peripheral surface. In addition, a convex portion formed in a protruding manner toward the above one peripheral surface at an end portion in the axial direction of the clutch retainer is disposed between a step surface formed on the above one peripheral surface or an end surface in the axial direction of a member fitted and fixed on this one peripheral surface and another step surface formed on the one peripheral surface or an end surface in the axial direction of the other member fitted and fixed to this one peripheral surface so as to regulate a displacement of the clutch retainer in the axial direction, thereby preventing the both end surfaces of this clutch retainer in the axial direction from contacting with a member which is rotated relatively to this clutch retainer.
Furthermore, in a rotation transmitting device corporation a one-way clutch therein of the present invention, a clutch outer race having a pair of flanges extending inward in the radial direction at the both ends in the axial direction thereof may be fitted and fixed into a middle part of the outer diameter side member in the axial direction with one of the peripheral surfaces serving as the outer peripheral surface of the inner diameter side member, and the inner side surfaces of the flanges which are opposited to each other may be approximated to face the both end surfaces in the axial direction of the clutch retainer.
As describe above, in case of the rotation transmitting device incorporating a one-way clutch therein according to the present invention, it is possible to prevent the both end surfaces in the axial direction of the clutch retainer from being brought into contact (sliding contact) with a member which relatively rotates with respect to this clutch retainer. More specifically, according to the present invention, when the clutch retainer has a tendency to displace in the axial direction, prior to the contact of the end surfaces in the axial direction of this clutch retainer with the portion rotating relatively to the clutch retainer, a convex portion provided on an end portion in the axial direction of this clutch retainer is brought into contact with the step surface formed on the above one peripheral surface or an end surface in the axial direction of the member which is fitted and fixed on this one peripheral surface. Since the step surface and the end surface are portions rotating with the clutch retainer, the step surface and the end surface do not rub the contact portion of the convex portion when the one-way clutch overruns. Thus, in case of the rotation transmitting device incorporating a one-way clutch therein according to the present invention, there is no possibility of abrasion of the both end surfaces in the axial direction of the clutch retainer or generation of frictional heat on the both end surfaces in the axial direction of the clutch retainer. For this reason, the abraded powder of the clutch retainer is not mixed into the grease for lubricating the one-way clutch, or this grease is not deteriorated by the heat. Consequently, it is possible to realize a rotation transmitting device incorporating a one-way clutch therein which maintains the state of lubrication of the one-way clutch over a long term satisfactorily and has a sufficient durability.
Furthermore, the structure may be arranged such that a gap is present all the time between the inner side surfaces of the paired round wheel portions formed at the both end portions in the axial direction of the clutch outer race and the both end surfaces in the axial direction of the clutch retainer. For this reason, this gap portion may be used as a grease pool, so as to conduct lubrication of the one-way clutch satisfactorily. More specifically, when the rotation transmitting device incorporating a one-way clutch therein is used, the centrifugal force acts upon the grease which is thick on the gap portion. Then, the grease thus receiving the centrifugal force is diffused uniformly on the inner peripheral surface of the clutch outer race. As a result, it is possible to sufficiently supply the grease into a gap portion between the surfaces of a plurality of locking members for constituting the one-way clutch and the inner peripheral surface of the clutch outer race. For this reason, the state of lubrication of the one-way clutch can be satisfactorily maintained for a long term, so as to realize a rotation transmitting device incorporating a one-way clutch therein which has a sufficient durability.